The invention relates to a method for treating aluminum slag obtained in the processing of aluminum.
This type of aluminum slag accumulates with the primary product of aluminum as so-called waste material, whereby the slag floating on the surface of the melt is scraped from the aluminum surface of the bath. This waste material contains diverse combustion products and released residue from the furnace infeed of the melting furnace in addition to metallic aluminum and aluminum oxide. According to the portion of aluminum contained in the waste material, the waste material is designated as skimmings (aluminum portion is >45%) or as dross (aluminum portion<45%). In so far as the waste material is supplied to a further processing step for recovery of the aluminum portion contained therein, the waste materials are underlying after their sloughing off from the bath surface based on the oxidation processes that use the effective surrounding atmosphere, which lead in addition to damaging gases in the working atmosphere of the melting furnace. Thus, it is known to scrape the waste material into a container and to cool this container under a protective gas atmosphere to a non-dangerous temperature level, which requires a correspondingly large amount of time.
Aluminum slags are also obtained with secondary production of aluminum from aluminum scrap, and herein in a still greater scope. In so far that in the frame of the salt bath processes used for secondary production, salt mixtures of NaCl and KCl are provided, so-called aluminum salt slags are formed, which likewise contain recoverable portions of aluminum. In particular, also these aluminum salt slags increase upon casting of the liquid rough melt to a direct reaction with the surrounding atmosphere, whereby on the one hand, the recovery of the aluminum portions from the aluminum salt slags is made more difficult, and on the other hand, dangerous gasses are released in the working area of the melting furnace.